When conducting foot surveillance on a busy street, the subject suddenly enters a crowded store. What is the most effective technique to maintain visual contact without being detected?

1. Use the 'pacing' or 'passing' technique, maintaining a natural flow and using other shoppers as cover.
2. Wait outside the store until the subject re-emerges.
3. Run into the store immediately after the subject, keeping directly behind them.
4. Call out the subject's name to make them stop.